Fatigue Life Prediction Via Strain Energy Density and Digital Image Correlation PDF Download

Author: Ying Kei Samuel Cheung
Publisher:
ISBN:
Category :
Languages : en
Pages : 0

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Book Description
The energy-based fatigue life prediction method estimates the fatigue life of a specimen, based on the theory that the total strain energy density dissipation required to cause monotonic quasi-static rupture is equivalent to the total energy dissipated in fatigue. The existing method is expanded to include predictions of the fatigue life of specimens with nanocrystalline coatings stressed at varying stress ratios. Digital image correlation is also used to demonstrate there is a region surrounding the fatigue crack initiation point where the strain energy density dissipation value deviates by a critical value from the median strain energy density dissipation value immediately prior to fatigue. This study represents one of the first instances in literature that the fatigue life of nanocrystalline-coated specimens has been quantified. As well, it provides a basis for estimating the fatigue life of coated specimens and an alternative indicator for predicting impending fatigue failure based on non-contact methods.

Author: Casey M. Holycross
Publisher:
ISBN:
Category :
Languages : en
Pages :

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Book Description
An improved fatigue life prediction method has been developed for Al 6061-T6511 test specimens using strain energy density as the criteria for assessing fatigue strength of plain and notched geometries at various stress ratios and loading spectra for cyclic lives from 10 to 105. The approach features interrogation at continuum and mesoscales using both a traditional fracture mechanics approach and a newly developed experimental procedure to determine strain energy density about machined notch roots in situ using digital image correlation. Testing revealed a critical strain energy density value independent of load ratio, notch geometry, and the effects of localized plasticity, indicating a new material dependent quantity to assess cyclic damage. The method better predicts lifetimes in low cycle fatigue than previously developed approaches, and has inherent capability to describe an endurance limit phenomenon. This study constitutes the most comprehensive investigation of strain energy density within the framework of the energy based fatigue life prediction method developed by Scott-Emuakpor et al., offering significant insight into cyclic damage behavior for all practical length scales and lifetimes.

Author: Darrell Socie
Publisher: SAE International
ISBN: 0768065100
Category : Technology & Engineering
Languages : en
Pages : 510

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Book Description
This book provides practicing engineers, researchers, and students with a working knowledge of the fatigue design process and models under multiaxial states of stress and strain. Readers are introduced to the important considerations of multiaxial fatigue that differentiate it from uniaxial fatigue.

Author: Cemal Basaran
Publisher: Springer Nature
ISBN: 3030577724
Category : Science
Languages : en
Pages : 452

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Book Description
This text describes the mathematical formulation and proof of the unified mechanics theory (UMT) which is based on the unification of Newton’s laws and the laws of thermodynamics. It also presents formulations and experimental verifications of the theory for thermal, mechanical, electrical, corrosion, chemical and fatigue loads, and it discusses why the original universal laws of motion proposed by Isaac Newton in 1687 are incomplete. The author provides concrete examples, such as how Newton’s second law, F = ma, gives the initial acceleration of a soccer ball kicked by a player, but does not tell us how and when the ball would come to a stop. Over the course of Introduction to Unified Mechanics Theory, Dr. Basaran illustrates that Newtonian mechanics does not account for the thermodynamic changes happening in a system over its usable lifetime. And in this context, this book explains how to design a system to perform its intended functions safely over its usable life time and predicts the expected lifetime of the system without using empirical models, a process currently done using Newtonian mechanics and empirical degradation/failure/fatigue models which are curve-fit to test data. Written as a textbook suitable for upper-level undergraduate mechanics courses, as well as first year graduate level courses, this book is the result of over 25 years of scientific activity with the contribution of dozens of scientists from around the world including USA, Russia, Ukraine, Belarus, Spain, China, India and U.K.

Author: Dino Anthony Celli
Publisher:
ISBN:
Category : Additive manufacturing
Languages : en
Pages : 0

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Book Description
The fatigue life prediction framework developed and described in the proceeding chapters can concurrently approximate both typical stress versus cycle (SN) behavior as well as the inherent variability of fatigue using a limited amount of experimental data. The purpose of such a tool is for the rapid verification and quality assessment of cyclically loaded components with a limited knowledge-base or available fatigue data in the literature. This is motivated by the novelty of additive manufacturing (AM) processes and the necessity of part-specific structural assessment. Interest in AM technology is continually growing in many industries such as aerospace, automotive, or bio-medical but components often result in highly variable fatigue performance. The determination of optimal process parameters for the build process can be an extensive and costly endeavor due to either a limited knowledge-base or proprietary restrictions. Quantifying the significant variability of fatigue performance in AM components is a challenging task as there are many underlying causes including machine-to-machine differences, recycles of powder, and process parameter selection. Therefore, a life prediction method which can rapidly determine the fatigue performance of a material with little or no prior information of the material and a limited number of experimental tests is developed as an aid in AM process parameter optimization and fatigue performance qualification. Predicting fatigue life requires the use of a previously developed and simplistic energy-based method, or Two-Point method, to generate a collection of life predictions. Then the collected life predictions are used to approximate key statistical descriptions of SN fatigue behavior. The approximated fatigue life distributions are validated against an experimentally found population of SN data at 10^4 and 10^6 cycles failure describing low cycle and high cycle fatigue. A Monte Carlo method is employed to model fatigue life by first modeling SN distributions at discrete stress amplitudes using the predicted fatigue life curves. Then the distributions are randomly sampled and a life prediction model is obtained. The approach is verified by using Aluminum 6061 data due to ample material characterization and previous life prediction analysis available in literature. SN life prediction is modeled via a Random Fatigue Limit (RFL) model using least square regression to determine the model coefficients. The life prediction framework is further developed by incorporating Bayesian statistical inference and stochastic sampling techniques to estimate the RFL model parameters. In addition, digital image correlation (DIC) is leveraged during experimentation to collect hysteresis energy as a novel method to monitor hysteresis strain energy or the assumed critical damage variable. Fatigue life prediction is performed in a dynamic way such that the life prediction model is continually updated with the generation of experimental data. The life prediction framework is applied to conventional Aluminum 6061-T6 and AM Inconel 718 and Titanium 6Al-4V. The framework is validated for life prediction and forecasting SN high cycle fatigue behavior using only low cycle fatigue data. The culmination of this work enables the rapid characterization of fatigue of AM materials by concurrently approximating the variation of fatigue life as well as high cycle fatigue behavior with low cycle fatigue data. The benefit of this framework is the significant reduction in experimental testing time, effort, and cost necessary to accurately assess the fatigue behavior of materials with limited prior information and specimen availability, such as in the case with AM Alloys.

Author: KC. Liu
Publisher:
ISBN:
Category : Cyclic fatigue
Languages : en
Pages : 18

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Book Description
A new method is proposed for multiaxial fatigue life prediction using correlation parameters based on virtual strain energy as a measure of fatigue damage on critical planes of fracture. The virtual strain-energy parameters are physically associated with two different modes of fatigue fracture planes. The critical plane leading to Mode I fracture is driven by the principal stress and strain, and the other, leading to Mode II fracture, is driven by the maximum shear stress and strain. The mode of crack initiation and propagation depends on material, temperature, strain range, and stress and strain histories, but not on the relative magnitude of the virtual strain-energy parameters. Biaxial fatigue data obtained from the literature were analyzed for Type 304 stainless steel tested at room and elevated temperatures and for SAE 1045 steel tested at room temperature under in-phase and 90° out-of-phase loading conditions. Comparisons are made between experimental data and theoretical predictions to show the effectiveness of the proposed method.

Author: Rachael C Tighe
Publisher: Springer Nature
ISBN: 3031174755
Category : Technology & Engineering
Languages : en
Pages : 96

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Book Description
Thermomechanics & Infrared Imaging, Inverse Problem Methodologies and Mechanics of Additive & Advanced Manufactured Materials, Volume 6 of the Proceedings of the 2022 SEM Annual Conference & Exposition on Experimental and Applied Mechanics, the sixth volume of six from the Conference, brings together contributions to this important area of research and engineering. The collection presents early findings and case studies on a wide range of areas, including: Test Design and Inverse Method Algorithms Inverse Problems: Virtual Fields Method Material Characterizations Using Thermography Fatigue, Damage & Fracture Evaluation Using Infrared Thermography Residual Stress Mechanics of Additive & Advanced Manufactured Materials

Author: Gert Heinrich
Publisher: Springer Nature
ISBN: 3030689204
Category : Technology & Engineering
Languages : en
Pages : 491

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Book Description
The book summarizes recent international research and experimental developments regarding fatigue crack growth investigations of rubber materials. It shows the progress in fundamental as well as advanced research of fracture investigation of rubber material under fatigue loading conditions, especially from the experimental point of view. However, some chapters will describe the progress in numerical modeling and physical description of fracture mechanics and cavitation phenomena in rubbers. Initiation and propagation of cracks in rubber materials are dominant phenomena which determine the lifetime of these soft rubber materials and, as a consequence, the lifetime of the corresponding final rubber parts in various fields of application. Recently, these phenomena became of great scientific interest due to the development of new experimental methods, concepts and models. Furthermore, crack phenomena have an extraordinary impact on rubber wear and abrasion of automotive tires; and understanding of crack initiation and growth in rubbers will help to support the growthing number of activities and worldwide efforts of reduction of tire wear losses and abrasion based emissions.

Author: Heinz Neuber
Publisher:
ISBN:
Category : Technology & Engineering
Languages : en
Pages : 226

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Author: Touhid Zarrin-Ghalami
Publisher:
ISBN:
Category : Elastomers
Languages : en
Pages : 153

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Book Description
This study investigates constitutive behavior, material properties and fatigue damage under constant and variable amplitude uniaxial and multiaxial loading conditions, with the goal of developing CAE analytical techniques for durability and life prediction of elastomeric components. Such techniques involve various topics including material monotonic and cyclic deformation behaviors, proper knowledge of stress/strain histories, fatigue damage quantification parameters, efficient event identification methods, and damage accumulation rules. Elastomeric components are widely used in many applications, including automobiles due to their good damping and energy absorption characteristics. The type of loading normally encountered by these components in service is variable amplitude cyclic loading. Therefore, fatigue failure is a major consideration in their design and availability of an effective technique to predict fatigue life under complex loading is very valuable to the design procedure. In this work a fatigue life prediction methodology for rubber components is developed which is then verified by means of analysis and testing of an automobile cradle mount made of filled natural rubber. The methodology was validated with component testing under different loading conditions including constant and variable amplitude in-phase and out-of-phase axial-torsion experiments. The analysis conducted includes constitutive behavior representation of the material, finite element analysis of the component, and a fatigue damage parameter for life predictions. In addition, capabilities of Rainflow cycle counting procedure and Miner's linear cumulative damage rule are evaluated. Fatigue characterization typically includes both crack nucleation and crack growth. Therefore, relevant material deformation and fatigue properties are obtained from experiments conducted under stress states of simple tension and planar tension. For component life predictions, both fatigue crack initiation approach as well as fatigue crack growth approach based on fracture mechanics are presented. Crack initiation life prediction was performed using different damage criteria. The optimum method for crack initiation life prediction for complex multiaxial variable amplitude loading was found to be a critical plane approach based on maximum normal strain plane and damage quantification by cracking energy density on that plane. The fracture mechanics approach was used for total fatigue life prediction of the component based on specimen crack growth data and FE simulation results. Total fatigue life prediction results showed good agreement with experiments for all of the loading conditions considered.